1. Field of the Invention
The present invention relates to a keyless entry system for a vehicle, configured to transmit an activation signal, such as an electromagnetic induction signal, for activating an electronic key from a vehicle-side transmission/reception device and to carry out predetermined control operations for vehicle-mounted devices, such as operations for locking and unlocking door locking devices, depending on predetermined encrypted signals transmitted from the activated electronic key.
2. Description of the Prior Art
In this kind of system, a detection distance within which the electronic key can receive the activation signal is required to be set properly. If the distance is not set properly, malfunctions may occur. For example, the door is not locked or unlocked although the person who holds the electronic key is near the vehicle.
In particular, the above-mentioned detection distance is very important in a system having an outside transmission antenna for transmitting the activation signal outside the vehicle interior and an inside transmission antenna for transmitting the activation signal inside the vehicle interior and configured to carry out control so that, when the person who holds the electronic key is outside the vehicle, the electronic key receives the activation signal from the outside transmission antenna and the door is locked or unlocked and so that, when the person who holds the electronic key is inside the vehicle, the electronic key receives the activation signal from the inside transmission antenna and the engine is started. In other words, if the detection distance of the outside transmission antenna is too short, a problem of not locking or unlocking the door occurs. In addition, if the detection distance of the inside transmission antenna is too long, even when the person who holds the electronic key is outside the vehicle, the electronic key responds to the activation signal from the inside transmission antenna, and the engine can be started, for example. Therefore, for example, a child not yet getting out of the vehicle may start the engine. This may cause a dangerous situation.
The above-mentioned detection distance changes depending on variations in the properties of the components of the system and also changes depending on the deterioration of the components with a lapse of time. In a conventional system, once the system is mounted on a vehicle, its detection distance cannot be changed. To change the detection distance, the system must be dismounted from the vehicle and then subjected to adjustment, replacement, etc.
The present invention is intended to solve the above-mentioned problems. A first object of the present invention is to provide a keyless entry system for a vehicle, capable of changing its detection distance even after the keyless entry system is mounted on the vehicle. A second object of the present invention is to provide a keyless entry system for a vehicle, capable of changing its detection distance by using members generally provided for the vehicle. A third object of the present invention is to provide a keyless entry system for a vehicle, the overall power consumption of which is reduced to save power.
In order to attain the above-mentioned objects, a keyless entry system for a vehicle in accordance with the present invention is configured so that a detection distance setting means for changing a detection distance within which an electronic key can receive an activation signal is provided on the vehicle and so that by carrying out predetermined operations the keyless entry system enters an adjustment mode wherein the detection distance can be changed by the detection distance setting means. With this configuration, the detection distance can be adjusted while the keyless entry system is mounted on the vehicle, whereby it is possible to attain a system causing no malfunction and ensuring high levels of security.
The predetermined operations to be carried out for the system to enter the above-mentioned adjustment mode are a predetermined number or more of times of brake pedal operations and a predetermined number or more of times of outer handle operations within a predetermined time, for example. Furthermore, in the adjustment mode, for example, one of different detection distances is selected sequentially each time the brake pedal is pressed, and by pressing and keeping the brake pedal in its pressed state for a predetermined time, the detection distance selected at that time is set as a new detection distance. With this configuration, members conventionally provided for the vehicle can be used without any modifications. The present invention can thus be attained without requiring new members.
In this type of system, a calling signal generally referred to as a reset signal is always transmitted before a coded encrypted signal is transmitted. In the present invention, a noise judgment section is used to make a judgment as to whether a received signal is a regular calling signal or not. The signal processing section of the system is activated only when the received signal is the regular calling signal. Hence, it is not necessary to always keep activating the signal processing section that requires high power consumption. As a result, the overall power consumption of the system can be reduced, and power saving can be attained.
Actual configurations and operations of the keyless entry system for a vehicle in accordance with the present invention will become apparent from the following explanations of a preferred embodiment.